Fabrics made of thermoplastic monofilaments have been used in a wide range of applications. Such fabrics are commonly used in the papermaking industry for transporting and dewatering the aqueous media there found. More broadly, such fabrics are used as filter media for wet, dry, hot and cold solutions and dispersions.
A fabric which includes a plurality of coils formed from a polymeric material is described in Shank, U.S. Pat. No. 4,381,612. The fabric was constructed by joining the coils using pintle or joint means, and the loops of the coils were filled by means of a single end monofilament, cabled monofilament, or multifilament yarn. The individual coil links were constructed from a thermoplastic such as a polyester monofilament in order have sufficient elasticity. Spiral fabrics are also disclosed in U.S. Pat. No. 4,395,308 for use as papermaker's fabric. These spiral fabrics were constructed by intermeshing spiral coils which were then joined by a pintle pin or hinge which was inserted between the intermeshed coils to hold them together. These pins have in the past, been prepared from metal and thermoplastic monofilament.
The permeability of spiral fabrics can be controlled by the thickness of the side lengths of the spiral wire and the thickness at the curved ends. Thus, if the wire thickness is greater or broader at the side lengths than the wire thickness at the curved ends, then a larger contact surface and hence a lower permeability fabric is obtained. Permeability of these fabrics can be further reduced by introducing filler materials into the spaces of the spiral fabric.
While the development of spiral fabrics has represented a significant advance in the field, the use of monofilament spiral fabrics in certain applications requires greater abrasion resistance than has heretofore been attainable using thermoplastic filaments.